A typical switching regulator converts a voltage from one level to another by controlling a switching element or elements to alternately store and release energy in an energy storage element, such as an inductive element. In operation, energy from an input power source is alternately stored in the inductive element and then released from the inductive element to thereby supply power to a load being driven. Many different topologies exist for switching regulators and may be generally classified as either step-up converters or step-down converters. Examples of step-up converters providing an output voltage Vout that is greater than a supplied input voltage Vin include Buck-boost and single ended primary inductor converters (SEPICs). Conversely, a Buck converter is an example of a step-down converter that provides an output voltage Vout that is less than the input voltage Vin.
In switching regulators, it is often desirable to measure an input current Iin coming into or being supplied from an input power source to the regulator during operation. This is particularly true when batteries are being used as the input power source and the amount of discharge current out of the batteries needs to be monitored and/or limited to, for example, extend the life of the batteries. Moreover, customers often have the need or desire to determine the power efficiency of their switching regulators, and to do so requires the ability to monitor the input voltage Vin and input current Iin supplied to the switching regulator along with the output voltage Vout and output current Iout provided by the regulator.
The power efficiency of a switching regulator is given by the output power Pout provided by the regulator divided by the input power Pin supplied to the regulator (Pout/Pin), where Pout=Iout×Vout and Pin=Iin×Vin. While customers would like to be able to determine power efficiency, they do not want to significantly increase the cost or complexity of their regulators to do so. Input voltage Vin, output voltage Vout and output current Iout are all presently monitored in most switching regulators, primarily because these parameters are easily measured and useful or required for controlling operation of the regulator. Input current Iin, however, is not typically monitored and needs to be in order to enable the power efficiency to be determined. The input current Iin to a switching regulator is a pulsed current not a direct current (DC) signal and accordingly is not easily measured, as will be appreciated by those skilled in the art. For the input current Iin an average value must be determined for use in calculating power efficiency with this average value being based upon the magnitude and duty cycle of the input current. This additional circuitry increases the complexity of circuitry forming the switching regulator, occupies valuable space in an integrated circuit in which the switching regulator or portions thereof are typically formed, and increases the cost of the regulator.
Alternative circuits and methods are needed for the input and output current and voltage measurements such that overall efficiency of a switching regulator can be determined.